1. Field of the Invention
This invention relates to a syringe. More particularly, this invention relates to a syringe having a retractable needle which can be releasably locked in operational and non-operational position.
2. Description of the Prior Art
The concern over protecting medical personnel from coming into contact with infectious diseases by contact with contaminated needles has led to the development of syringes with retractable needles. The recent concern over the avoidance of being infected with the AIDS virus has led to even a greater importance being placed in the use of retractable needles.
U.S. Pat. Nos. 4,650,468 and 4,643,199 are examples of syringes which have been developed so as to allow for a potentially infectious needle to be withdrawn into the syringe's interior after use.
Each of the above two United States Patents involve the formation of grooves in an inner cylindrical member and the formation of locking lugs on an outer cylindrical member. To position the needle in an operational position, the inner member is first rotated such that the lugs of the outer member become disengaged from a first locking section of the inner member's grooves. Subsequently, the outer member is drawn along a straight line section of the inner member's grooves. Thereafter, the inner member is again rotated with respect to the outer member until the lugs of the outer member become locked within a second locking section of the inner member's grooves. To retract the needle attached to the inner member after use, the same procedure is followed only in reverse.
Thus, in the above two patents there is a requirement that the grooves and lugs be placed in alignment during the process of locking the needle into operational position and during the process of retracting the needle after use. This alignment requirement presents a problem when quick positioning of the needle is essential such as in an emergency situation. There also exists the possibility that initial problems in alignment can result in the user becoming panicked which could lead to even further time delays.
Moreover, as the various components of the syringe are likely to be rotated with respect to one another, there also exists the problem of unwanted release. That is, during the use of the syringe the inner and outer members might inadvertently become aligned along the straight groove portion and create an accident due to undesirable movement of the needle.
U.S. Pat. Nos. 4,507,117 and 4,675,005 illustrate syringes having retractable needles which are releasably connected directly to the plunger by way of rotation. Accordingly, these syringes suffer the same problems noted above with regard to rotative attachment and detachment.
Haller U.S. Pat. No. 4,692,156 shows a retractable needle which is locked directly onto the sealing plug of a plunger. Haller, in one embodiment utilizes a "snapping" connection between the needle and plug. This "snapping" connection is essentially non-detachable and thus Haller provides a one shot device. That is, inadvertent attachment before use cannot be remedied. Therefore, either direct contact is made with the needle to separate the needle from attachment with the plug or the syringe is discarded as useless.